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Rod properties, line speed, and casting motionsWhe - Questions

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Bill Hanneman
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Rod properties, line speed, and casting motionsWhe - Questions

Post by Bill Hanneman »

Whether or not this can be done is an open question. Nevertheless, before one can approach this problem, several definitions must be agreed upon.
1. Most importantly, what is meant by line speed, and how is it to be measured?
As I see it, the casting motion starts with line speed=0. As the rod is accelerated, the speed of the far end of the line increases and simultaneously the rod is “loaded”. As the caster begins his “stop”, the speed due to the initial accelleration decreases while additional speed is introduced by the rod “unloading”. Ultimately, the speed of the line (at the rod tip) exceeds that of the tip itself and the loop is formed and the far end of the line progresses towards the target.
However, the near-end of the line is attached to the reel and again has a speed of zero while the other end is unrolling at an ever increasing speed, and according to theory can reach the speed of sound at which point the fly breaks off.
So my question is, “How is line speed to be measured.?
2. What constitutes a casting motion and how can it be described in physical terms?
gordonjudd
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Post by gordonjudd »

Whether or not this can be done is an open question.

Bill,
Do you understand what Grunde's and Merlin's forced harmonic oscillator model of casting is all about?

The results they predict for line speed using their model compare very well to measured values taken on different rods with different casting motions, so I think they have shown it can be done quite nicely.
However, the near-end of the line is attached to the reel and again has a speed of zero while the other end is unrolling at an ever increasing speed, and according to theory can reach the speed of sound at which point the fly breaks off.

To get this result, your "theory" is neglecting the effects of aerodynamic drag on the line and fly. The real situation is much more complicated as discussed here.
What constitutes a casting motion and how can it be described in physical terms?

If you have not seen it before, Jason Borger's and Grunde Lovoll's article on The Rod and the Cast is a an excellent resource for finding answers to your questions.

Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
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Merlin
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Post by Merlin »

Bill

The key information is the rod butt angle history. From that we can predict rod response if we know how its frequency changes with load.

Merlin
Fly rods are like women, they wont´play if they're maltreated.
Charles Ritz, A Flyfisher's Life
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